Rotary line switch



July 9, 1929. w 1s 1,719,862

ROTARY LINE SWITCH Original Filed May 9, 1,925

Barnard D. [11.77.2115

Patented July 9, 1929.

UNITED STATES PATENT OFFICE.

BERNARD D. WILLIS, OF CHICAGO, ILLINOIS, ASSIGNOR TO AUTOMATIC ELECTRIC INC., 013 CHICAGO, ILLINOIS, A CORPORATION OF DELAWARE.

ROTARY LINE SWITCH.

Original application filed May 9, 1925, Serial No. 28,995.

Divided and this application filed April 12,

1928. Serial No. 269,489.

This invention relates in general to automatic switches, but is concerned more particularly with switches of the automatic hunting type, commonly known as line switches. Switches oi this character are used in automatic telephone systems, individual to each subscribers line, and when used in this situation the functionv of each line switch is to select a trunk to an idle succeeding switch, for example, a first selector, and con nect the suhscribeids line thereto.

The object of this invention is to provide new line switches of the rotary type having a home or normal position in which the switch wipers normally rest. When a call is initiated, the wipers are rotated in a forward direction in search of a trunk to an idle succeeding switch, and come to rest when they engage the contacts at which the conductors of a trunk to an idle succeeding switch terminate. When the call is over with and the switches associated with the talking connection are released, the wipers of the line switch are again automatically rotated in the forward direction until they reach the home position.

The utility and advantages of the home-position type rotary line switchare commonly known to those familiar in the art, so no discussion of these subjects is given.

The new line switch which forms the subject matter of this invention is illustrated by means of the usual schematic circuit diagram in the figure of the accompanying drawing.

Referring to the drawing, there is shown a snbscribers telephone substation A with a line terminating at a central automatic exchange in the individual line switch LS, which is of the home-position rotary type. At the banks of the line switch access had to first selector switches. These selector switches may be of any well-known type, the vertical and rotary, for example, and are responsive to the first digit dialled by the calling subscriber. One of these selector switches is indicated by reference letter S, only those elements having to do with the operation of the line switch being shown. A call from the substation A to another subscribermay be extended through line switch LS, selector S, and through other selectors, depending on the size of the system, and through a connector switch to a called subscriber.

To initiate a call, the subscriber at substation A removes his receiver. Removing the receiver at substation A places a direct current bridge across the line conductors 2 and 8, thereby closing a circuit for the line relay 5 of the line switch LS. This circuit may be traced from the grounded resting contact and armature 10, line conductor 3, through the substation A, line conductor 2, armature 7 and the resting contact, through the winding of line relay 5 to battery. The wipers 23, 24, 25 are normally resting on the home-position contacts 20, 21, 22, respectively. Upon the energization of line relay 5, at armature 11 and the working contact ground is placed. on the private normal conductor 16 connected to the private contact in the connector banks to protect this line from being connected with y some other calling line. A circuit is also completed from ground. by way of armature 11 and the working contact, home-position contact 21, wiper 24, working contact and armature 12, armature 15 to the magnet 6. The stepping magnet is arranged to rotate the switchwipers on its return stroke, i. a, when it deenergizes. Upon the first deenergization ofstepping magnet 6, the wipers 23, 24, 25 are rotated off the home position to the next set of bank contacts. Cam 14 also rotates and closes spring 13, thereby preparing the return stepping circuit, to be described later. If the first selector accessible at this set of contacts is busy, there will be ground on the private contact engaged. by the private wiper 24: and the ground will be maintained on the unction oi. the switching relay 4; and the arn'iature 15 oil: the magnet 6. The circuit for the stepping magnet 6 is still maintained and on the next deenergization of the magnet 6 the wipers will be rotated to the next set of bank contacts. This stepping actionwill continue until the wipers 23, 2%,25, engage a set of contacts leading to an idle selector switch, the idle condition being indicated by the absenceot ground po-. tential on the private contact.

It will be assumed that selector S, accessible at the line switch bank contacts 26, 27, 28, is the first idle selector found. Under this condition there is no ground on bank contact 27 and the winding .01": switching relay l is no longer short-circuited and the relay will energize. The circuit of the stepping magnet is thus opened at armature 9, and as a result the wipers 23, 24:, 25 remain engaged with the .busy nor idle to connectors.

bank contacts leading to selector S. The energization of switching relay 4 also results in the opening of a point 8 in the return-stepping circuit, to be described later, and in the operation of armatures 7 and 10 which disconnects the line conductors 2 and 3 from the line relay 5 and ground, and connects them by way of wipers 23 and 25, bank contacts 26 and 28, armatures 33 and 35 and the resting contacts, through the upper and lower windings of the line relay 31 of the selector 8 to battery and ground, respectively.

The line relay 31 of the selector S energizes over the above-traced circuit and closes a circuit for the release relay 32 at armature 36. Release relay 32 operates and places ground on conductor 38 at armature 37, thereby supplying a holding ground for the switching relay 4 of the line switch LS and a protecting ground to conductor 16, by way of bank contact 27 and wiper 24:, before line relay 5. has had time to fall back.

The release. of the line switch is brought about by the removal of ground from the conductor 38 in the well-known manner. The switching relay 4 is deenergized and its armature springs are restored to normal. A return-stepping circuit is now completed for the stepping'magnet 6 from ground by way of armature 11 and the resting contact, closed springs 13, the resting contact and armature 8,

through the interrupting contacts 15 of the stepping magnet 6, to the magnet. The stepping magnet 6 will now operate to rotate the wipers 23', 24, 25step-by-step in the forward direction until they reach the home position.

' At this position the cam 14 will again open the springs 13, thereby opening the return stepping circuit of the stepping magnet 6. Consequently, the wipers will remain resting in the home position. v

During the homing movement of line switch LS, the associated line will test neither This will be bestunderstood by considering the operation of an ordinary connector, for example, a connector such as that shown on page 38 and described in Chap. VII of H. E. Hersheys book Automatic Telephone Practice, third editioni It will be noted that the test circuit of theconnectorfirst includes the busy relay and is later'switched over to the wiper cut-oii" relay. If the, line is in use, the busy relay operates from direct ground which is connected to the release trunk at the lineswitch, selector, or connector in the usual manner.

'If'the lineis not in use, the Wiper cut-off relay of theconnector and the switching relay of'theline switch such as relay 4 operate in series from battery through the stepping magnet'6. However, if'the wiper-s of the connector are set on the line contacts duringthe homing movement of the switch, the testing operations are somewhat different. At this time the releasetrunk is connected to ground through the relatively high resistance of relay 4. The busy relay of the connector will not operate in series with relay 4; and consequently the connector will not return the busy signal. hen the test circuit is switched over to the wiper cut-oil relay in the usual manner, this relay does not operate since it is shunted by the ground on the junction of the stepping magnet and switching relay ot the line switch. hen the line switch wipers reach home position, otl normal contacts 13 open and disconnect the ground from the above junction point and the wiper cut-otl.' and switching relays operate as previously described. It is obvious from the foregoing that the line may be selected but cannot actually be connected with during the interval in which the line switch is restoring to normal.

that is claimed is:

1. In a telephone system, a rotary line switch of the homing type, an incoming test conductor for the line switch, in vans for placing either of two different test potentials on said conductor to indicate a busy and an idle condition, respectively, and means including cam controlled oft-normal contacts for causing said conductor to test neither busy nor idle during the home returning movement of the switch.

2. In a telephone system, a homing type rotary line switch, an incoming test conductor, means for placing battery potential on said conductor when said switch is in its home position, means for placing ground potential on said conductor when said switch is seized, and means including a pair of fixed oft-normal contact springs for removing said battery potential from said conductor when said switch is returning from an oil-normal position to its home position.

3. In a rotary line switch of the homing type, a switching relay, a magnet, one terminal of the switching relay being connected to one terminal of the magnet, an incoming test conductor connected to the other terminal of the switching relay, means vtor placing a guarding potential on said test conductor, means including a single pair only of back contacts of the switching relay for placing a similar potential at the juncture point of the relay and the magnet for causing the magnet to operate the switch, and means for removing said first-mentioned potential and for reapplying said second-mentioned potential to cause the return to normal movement of the switch, whereby said switch is unguarded but not seizahle during the return to normal movement of the switch.

4. In a rotary line switch of the homing type, a switching relay, a magnet, one terminal of the switching relay being connected to a terminal of the magnet, an incoming test conductor connected to the other terminal of: the switching relay, means including a front contact of the switching relay for placing a guarding potential on said test conductor, means including shaft controlled contacts for placing a similar potential at the juncture point of the relay and the magnet for causing the movement of the switch, and means for removing said first-mentioned potential and for reapplying said second-mentioned potential to cause the return to normal movement of the switch, whereby during said movement the switch is unguarded but not seizable.-

51 An automatic trunk hunting switch of the homing type including a motor magnet for moving the switch, a switching relay, a line relay, a test wiper, and a pair of oft-normal contacts, one terminal of said switching relay being connected to one terminal of said magnet, a test circuit extending from the wiper through a back contact on the switch ing relay and a front contact on the line relay in series to the juncture of the switching relay and magnet, and a homing circuit for the switch extending through a series circuit including ofi-n0rmal contacts, hack contacts on the line relay and back contacts on the switching relay.

6. In an automatic trunk hunting switch, a source of potential, a motor magnet, a switching relay, and an incoming test conductor all connected in series in the order named, a test wiper, means for connecting said wiper to the juncture point of magnet and relay for controlling the trunk hunting movement of the switch, and means inclependent of the wiper for placing a characten istic potential at said uncture point for controlling the home returning movement of said switch, said potential being effective to prevent the operation of the switching relay over the incoming test conductor upon the seizure of the switch.

7. In a trunk hunting switch having a home position, a switching relay, a motor magnet, a test wiper, means for connecting the test wiper to the magnet and to the switching relay for controlling the trunk hunting movement of the switch and for preventing the operation of the switching relay, and means independent of the wiper for connecting a characteristic potential to the magnet and to the switching relay for operating the magnet to return the switch to its home position and for preventing the operationof the switching relay during the heming movement of the switch.

8. In a rotary line switch of the homing type, a switching relay, a magnet, one terminal of the switching relay being connected to one terminal of the magnet, a test wiper, means for placing a characteristic potential at the juncture of the magnet and the relay for operating the magnet, said means including either of two circuits one of which includes the test wiper and the other excludes the wiper.

In witness whereof, I hereunto subscribe my name this ninth day of April A. D. 1928.

BERNARD D. WILLIS. 

